1. Field of the Invention
The present invention generally relates to a radiation detecting apparatus, a manufacturing method thereof, a scintillator panel and a radiation detecting system which are used for a medical diagnostic device, a nondestructive inspection device and the like, and more particularly to a scintillator panel, a radiation detecting apparatus and a radiation detecting system which are used for X-ray radiographing and the like. Incidentally, in the present specification, the description is given on the basis of the supposition that the category of a radiation includes an electromagnetic wave such as an X-ray and a γ-ray.
2. Related Background Art
In recent years, the digitization of X-ray radiographing has been accelerated, and various radiation detecting apparatuses have been announced. Their systems are roughly divided into two types of a direct system and an indirect system. The direct system is a type which directly converts an X-ray into an electric signal, and reads the converted electric signal. The indirect system is a type which once converts an X-ray into visible light and then converts the converted visible light into an electric signal to read the converted electric signal.
FIG. 11 is a sectional view of a radiation detecting apparatus of the indirect system disclosed in U.S. Pat. No. 6,262,422. In the drawing, a photoelectric conversion unit (light receiving unit) is formed by two-dimensionally arranging a plurality of photoelectric conversion elements 102 on a substrate 101, and the upper parts of the photoelectric conversion elements 102 are protected by a sensor protecting layer 104. Wiring 103 extending from the photoelectric conversion elements 102 is connected to a bonding pad portion (electrode extracting portion) 106 (a unit including the substrate 101, the photoelectric conversion elements 102, the sensor protecting layer 104 and the wiring 103 is also called as a “sensor panel”, a “photoelectric conversion panel” or the like).
On the sensor protecting layer 104, a phosphor layer 111 made of CsI:Tl of a columnar crystal is formed as a wavelength conversion body converting a radiation into the light which the photoelectric conversion elements 102 can sense. The humidity proof protection of the phosphor layer 111 from the exterior is implemented by a phosphor protecting layer 112 consisting of an organic film made of poly-para-xylylene (trademark name: Parylene) having a thickness of about 10 μm, a reflecting layer 113 made of aluminum, and a protecting layer 114 made of Parylene. The reflecting layer 113 made of aluminum is provided for reflecting the light proceeding to the opposite side of the photoelectric conversion unit from the phosphor layer 111 and for leading the reflected light to the photoelectric conversion unit. The reflecting layer 113 is in a thin film state having a thickness of a submicron level by a vapor deposition method or the like. A reference numeral 115 denotes a covering resin for preventing the exfoliation of the phosphor protecting layer 112.
The radiation detecting apparatus shown in FIG. 11 converts entering X-ray information into a two-dimensional digital image by the configuration described above as follows. That is, an X-ray entering the radiation detecting apparatus from the upper part of the drawing transmits the protecting layer 114, the reflecting layer 113 and the phosphor protecting layer 112, and is absorbed by the phosphor layer 111. After that, the light emitted from the phosphor layer 111 reaches the photoelectric conversion elements 102, and the electric signals converted by the photoelectric conversion elements 102 are read by a not shown external circuit through the wiring 103.
The above-mentioned material called as Parylene constituting the humidity proof protecting layer (composed of the phosphor protecting layer 112 and the protecting layer 114) on the phosphor layer 111 is stated in “Parylene coating system”, Three Bond Technical News, Three Bond Co., Ltd., Sep. 23, 1992, vol. 39, pp. 1-10. Parylene can be acquired as follows. A raw material called as di-para-xylylene (dimer) is heated and sublimated under a low pressure, and then a para-xylylene radical gas in a state of being heated to about 600° C. to be thermally decomposed is introduced to the adherend. Thereby, polymeric para-xylylene having a molecular weight of about 500,000 is condensed and polymerized to be acquired as Parylene.
However, the Parylene used as the material of the phosphor protecting layer in the prior art radiation detecting apparatus mentioned above is very reactive in a para-xylylene radical gas state in which one kind of dimer is thermally decomposed. Consequently, reactions sometimes advance in a gaseous state depending on changes of the temperature and the pressure in the system, and the produced organic film may become a heterogeneous film or have generated projections owing to by-products on the surface thereof. Such states will roughen the reflection surface of the reflecting layer 113 formed in the upper part of the phosphor protecting layer 112, and image defects may be caused in the worst case.
In the view of the problems mentioned above, it is an object of the present invention to provide a radiation detecting apparatus including a phosphor protecting layer which does not make the reflection surface of a reflecting layer on a phosphor layer produce structural disorder, and being capable of suppressing the generation of image defects.